This invention relates generally to three dimensional conductive structures and methods of making the same, and, more specifically, to the structure and manufacture of a metal laminated structure for a housing of an electrical connector.
Due to advances in processor technology, signal transmission rates between electronic devices and components is increasing. With increased signal transmission rates, the need for effective shielding of signal contacts in electrical connectors interconnecting the electrical components is of greater importance. In at least some connectors, such as, for example, ball grid array (BGA) sockets which connect a microprocessor to a printed circuit board, metallized housings are advantageous. The metallized housing shields the signal contacts and prevents cross-talk, as well as provides a larger ground path than is typically available in non-conductive connectors.
Conventionally, plastic housings have been manufactured via injection molding processes. These housings are subsequently metallized using a variety of techniques. Manufacturing the metallized housings, however, is problematic for increasingly miniaturized connectors. Thin walled constructions tend to be weak, and shrinkage or processing variations can frustrate dimensional specifications, flatness requirements, etc. Additionally, injection molded plastic tends to present mismatched thermal coefficients of expansion relative to the integrated circuit materials used and the thermal expansion properties of circuit boards with which they are used. The disparate thermal expansion properties of the metal and plastic creates thermal stress in the structure which may produce reliability issues. In particular, in a surface mount device, such as a BGA socket connector, the thermal stress may negatively impact the soldered connection to the circuit board.
To avoid limitations of injection molding processes for smaller structures, metal laminates are sometimes bonded together via a diffusion bonding process. Diffusion bonding, however, takes place in a vacuum and under controlled pressure conditions at regulated temperatures at or above approximately 80% of the metal homologous temperature for a sufficient time to form a sold state diffusion bond between the laminates. For most applications, diffusion bonding is an equipment intensive, time consuming, and prohibitively expensive process that is not feasible for high volume, low cost electronic components and connectors.
Another technique which may be used to form conductive structures is metallization of monolithic polymer materials. Achieving desired specifications (e.g., minimum wall thickness, cavity sizes, flatness and coplanarity requirements) for electrical connectors using such materials and methods, however, is exceedingly difficult.
Adhesive bonding may be used to join thin metal laminates to construct small structures. Adhesives, however, are typically not electrically conductive, and therefore impact the electrical properties of the structures. Conductive adhesives are expensive and may produce undesirable in the electrical properties of the housings.
It would be desirable to provide an economical structure for electrical connectors which avoids these and other issues.